Machine for sharpening the points of twist drills or the like



May 7, 1940.

MACHINE FOR SHARPENING THE POINTS OF TWIST DRILLS OR THE LIKE Filed Nov 29, 1 935 J. ARMAND 2.199.773

Patented May 7, 19 40 UNITED STATES I PATENT OFFICE Mancunian-unison InGu-nanlluduilfll Quote. (an-2m mtialpartofthemflntistosayitspoint,

ensnretheperformanceofthseoperafionswithe mrttheattendanthavingtotakespeclalpremutionsandbeing,tothisexteht,asharpeningspecialist.

Itisknown, ontheotherhanithat theintersectionofthetaperedsurfacesofthe twocdtting edges andwhich'ssituatedattheapex oi'a twist drillorthelikejsnotonlyinoperativebut, onthe contrarmmnstitutesanohstabletothe penetraiion of the tool.

In fact, said intersection between the tapered surfacesofthetwo cuttingedgesformstheblimt edgeofanobtusedihedralanglewhicminstead :3 of asststingthe penetrationofthe drill intothe metahexerts adragmthesurface thereofattaining,inthemseofdrillsof large diameter, almost An object of the invention is to convert this so intersecting edge into two leading and cutting edges by away the two spices to leave two inclined surfaces meeting in asingle apex.

That is' to say, in order to obviate the difflc'ulties previously met with the usual tapered surfam 35 obtained by present grinding methods, said tapered surfaces are each reduced by grinding the trailing edge thereof to a slope materially steeper than that of the original surfaces, and in a radial direction forming a substantial angle with the 40 initial blunt intersection.

Said finishing operation is effected in. two

stages, first on one tapered surface, continuing until said steeper sloping surface reaches the geometric center of thedrill tip, thus removing in 5 one operation one half of said blunt edge. The drill is then revolved 180; around its axis, and a similar grinding operation is effected on the trail-' ing edge of the opposite tapered surface, until the geometric center of the drill tip is reached from 50 the other side, thus removing in a second operation the second half of said initial blimt edge, and leaving four tapered surfaces meeting in one point at the geometric center of the drill tip. The drag on the metal due to the initial blunt edge is thereby eliminated and, moreover, this operation proactimof whidiisaddedtotlntofthemigimlmammt tingedges. Thisgreatlyfadlitatesthepmetmtimofthedrillintothemetoltohedrilledto- 5 nofurther taidency-to be deflectedalong the metallic sn'face.

This secondpr flnishinggrinding operation, whichensunsasuhstantiolincreaseintheefliciencyofthetooLmayatpresmtbeelfectcdtu 1o hand,andisanopelatmnrequiringsuhstanflal skill.

Themachineformingthesubjectofthemmt invention is of the type cums-king a grinding wheeLmeansfortruingsudiwhee1andachmk li fm'canyingthedrilladaptcdtohaveacntting feed imparted to it by haul operated mrn'age meansandhasforitsobjecttofinishorcomplete the sharpening of thepoints of twist drilk by making it posible to eliminate, in a second or m bluntedgefromthetipofsaiddrillwithamathcmaticaliyesactprccisionwithouttheskilloftheatiendantbeingconsidered.

Oneofthecharacterisfissoftheinventionresidesinthefact that thetwistdrill,'wheninthe grindingposilimisheldinsuchmannerinthe drillholder that its axisor center-line liesinthe -plane of the radial working face of the grinding wheel, and at a substantial angle with the direc- 7 tion in which it is fed towards said grinding wheel; and, moreover, in that the geometric center of the drill tip moves on a line tangent to the peripheral working face of the 'wheel. In this maner, the sharp edge produced by the intersection of the radial and peripheral working facesof the grinding wheel cuts into the previously formed tapered surface'which backs one of the cutting edges of the drill along the axis of said drill; and,

in so doing, the radial working face forms an auxiliary cutting edge, while the-peripheral working face of said grinding wheel cuts a bevel or inclined surface into the trailing edge of said initial tapered surface to a'materially steeper slope than that of said tapered surface.

Another essential characteristic of said machine lies in that truing means are provided for trimming the radial and peripheral working faces of said grinding wheel, said radial truing means being adapted to trim the radial working face exactly in a plane passing through the-axis of the drill when the latter is set in, .its drill holder in the grinding position; and said peripheraltruing means being adapted to trim the peripheral working race of said grinding wheel in such manner as to keep the cutting edge of the grinding wheel tangent to the line of travel of the geometric center of the drill tip. To these ends, said radial truing means are mounted in flxed space relation with respect to said drill holder, and provided with a trimming tool, such as a diamond, the cutting edge of which lies in a plane containing the axis of said drill when in its holder, said plane being parallel at all times to that of the radial working face of said grinding wheel and coinciding therewith when the drill is in the grinding position. Furthermore, said peripheral truing means are so disposed that they can be fed in a line parallel to the axis of rotation of said grinding wheel, and in such manner as to adapt it to trim the peripheral grinding face to make thelatter exactly tangent to the line of travel of the geometric center of the drill tip.

Another characteristic of this invention lies in that, when the grinding wheel has been trimmed radially and peripherally, the working positions of the two diamond cutting edges of said radial and peripheral truing means are functions of two limiting and previously adjusted stops or abutments, one of which stops defines simultaneously the plane of the trimmed radial working face of said grinding wheel and of the axis of the drill in its drill holder; while the other stop defines the cylindrical working surface of the grinding wheel in such manner that it must be tangent to the line of travel of the geometric center of the drill tip.

Thus said drill is made to follow automatically the wear of the grinding wheel in such manner that its axis or centerline remains in a fixed position relative to the radial and peripheral working faces of said grinding wheel, without depending upon the skill of the operator.

A further characteristic of this invention lies in that means may be associated with said drill holder, for the purpose of automatically positioning said drill axially in said holder in such manner that the geometric center of the drill tip will lie in a plane parallel to the axis of the grinding wheel and passing through the cutting edge of the peripheral truing tool, in order to cause said drill to move with its center always on a line tangent to the periphery of the grinding wheel, said positioning means being removable, once the drill has been clamped, in its with the radial working face of the grinding- The attached drawing shows, by way of example only, one embodiment of a machine for sharpening the points of twist drills or the like according to the characteristics specified above, as well as showing diagrams of the drill sharpened ac- I cording to known machines and by the machines according to the present invention. 7

Fig. 1 and Fig. 1 are views in elevation and in plan of the point of a twist drill sharpened in the ordinary way and having a blunt and substantially straight edge A-B formed at the apex ofthe tool; by the intersection of the tapered surfaces 8 and S. This intersection ed e A-B,

as is known and commonly agreed, constitutes an obstacle to the penetration of the tool, as stated above.

Fig. 2 and Fig. 2 show also views in elevation and in plan of the same drill point, but after sharpening on the machine forming the subject of the application with the blunt edge to be eliminated lying in the plane of the radial working face of the grinding wheel. This operation produces two cutting counter edges A0. and OB, O representing'the neutral point, said cutting counter edges A and OB lying substantially in a straight line.

Fig. 3 and Fig. 3 represent two views of the same drill of which the sharpening operation has been performed after turning the drill in such a way that the edge AB (Fig. 1) forms an angle a with the radial working face of the grinding wheel, which in elevation gives a noticeable inclination to the cutting edges A'O and OB relatively to the perpendicular to the axis of the drill, thus constituting an angle of which the apex is exactly at the axis of the drill in order to facilitate its centering and its correct penetration on a simple punch mark.

Fig. 4 is a view in elevation of the face of. the

machine.

Fig. 5 is a lateral elevation and Figs. 6, 7 and 8 are three different views of the device for axially and radially positioning thetwist drill in its mandrel or chuck. v

In its preferred embodiment, the sharpening machine comprises a frame i at the upper part of which there is mounted a grinding wheel 2 driven at a suitable peripheral speed. On this frame there can be displaced vertically a bracket member 3 mounted in suitable guides and supporting two movable tables 4 and 5, one pro vided with a support 6 destined to receive the radial truing tool and the table 5 being provided with a support 9 for'the peripheral truing tool.

The table 4 is operatedbymeans of the'lever 8 while the table 5 is controlled by the hand wheel H. As shown clearly by Figs. 4 and 5, the diamond tool 1 is destined to trim the radial face of the grinding wheel 2 while the diamond tool Ill trims its peripheral face. The two tables 4 and 5 are thus displaceable in perpendicular planes.

The diamond tool 1 is fixed on the movable upper table 4 in such a way that --its point is situated exactly in the plane passing through the axis of the drill and parallel to the radial face of the grinding wheel. The point of the diamond tool l0 fixed on the carriage 5 is situated exactly in the line of intersection of the plane parallel to the plane of motion of the lower table 5 and passing through the point of the.

drill with the perpendicular plane passing through'the axis of the grinding wheel.

The upper table 4 supports the drill-carrying mandrel or chuck l4 inclined-' relatively to the plane of motion of the upper table 4 and provided with a positioning abutment l2 with a counter point l2. The drill to be sharpened is fixed between the jaws of the mandrel or chuck and may be operated through thedesired angles of rotation by means of an operating wheel I3.

The table 5 is provided with an abutment ii of which the position may be regulated by means of a micrometer screw. This abutment stops the movement of the table at theexact point where the diamond 1 is tangential to the front 'face of the grinding wheel. A second abutment I,

nfthegrlndingwheelunderthesame asatfm'thefrontfacebymeansofthe' diamond I. This second abutment l6 comesinto actimdm'ingtheoperationoithehandlell for the purpose of setting the aiore-mentioned initial hhmt edgeAr B at the required angle-p dstinedforthevertiealregulaflonanditstops thevertimlmovementofthesystemattheexaet point where the diamond is tangential to the periphery oithegrindingwheel.

From the above dseription, it will be seen' thattherespectivepositionsoitheabutments and lideterminewithgreatpleeisionthepo sitieminspaceoftheradiaiandperipheralworkingiaees ofthewhee12,henee.the of their intersecting edge; fm'thennore, thetwistdrilwhenelampedinitsehunklflis sopesitienemfirshthatitsaxisliesintheplane ofthemdialwmkingiaeeoisaidwheel; and secondly, that the geometric center or apex '"oiitsiipautematimilyfellnwsanyprodueedbyradiailandperiphemltnfingopemtims intheloeationoisaidiuedgeofthe radial and faces, in sueh mannerthatthe motionoitheuppertahlel eausessaidgeemetrieeenterofthedrilltipto iollowaiinelymgintheplaneofthemdial gfinding face and tangent to the peripheral iaee. I Inerdertoensm'ethedrmhehiinthe axiallyandradiallyem'rect-n, asdefined hereinbetmwithmpeettnsaidmmalandperipheralworking fans ofthegrindingwheei 2, thisinventienpfovidwposimeamwhieh mayberemovedaiterthedfillhasbeeneorreetlypositinned and clampedinits holder, so that said positiening'means shall not interf with the mem One emtofsuch fllustratedinfies-fiflianda. Inthisemhodiment, said means comprise a hdlow V-shaped block I! adapted to fit exactly over theiipoithedrillasthelatterisshapedwhen ground by present methods, the vertex of said V being adapted to coincide with the geometric center of the drill tip. Said V-block is mounted mtatably in a blanket support I! piv-' otedtotheuppertahleLthiapurmseofwhich.

support is to fix invariably the relative position oftheeenterofthedrilltinwithrspeetto table 4, and hidireetfly with respect to-the perlpheraltmingtool ll. Said V-hloekismmmted inits supportlsinsuehmannerthatitmaybe revolvedthereinarmmdanaxiseifineidingwith thatoithetwistdrillinitsehuek. A scale enables the flpmtm'to determine accuratelytheangularposifionofthedrillinitschuck,

withiespecttotheradialwotkingfaee ofthe grinding wheel; andalocking device clamps said V-hleek liinsaidpositum.

-wnenuaisdesiredm osimntnedrmsmm suppurt liisswungintoitsopemtive whereinthevertexoftheV-hlockisatthesame height above the plane of the table [as the cuttingedgeoftheperlpheraitruingtool ll,and inthepl anecontainingthe'axisofthedrllland parallel'tothatottheradialworkingiaeed saidgri'ndingwheeli. Thedrillisth'enmnvedaxiallyandradiallyintheehuck lluntiliistip fitsperfectlyintotheV-hloek; itisthmelamped inthe ehuchandtlmsupport liisswungheek untflitlies on'table tout of them otthe '(ming means ispermitstheadee tobe'gmundwifllmedcel inelmedtomeamtherandrdafivelytoaphue.

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1. m flieslnrpmingoftwistdrillsby n erafimthelfluntukefiunyflleflpuljm drillspreviouslygmundhymnand replacing said-hluntedgebyt'o l; Lem.

ldnatiomaflmme,aeylindl'iealliedv wheel havingmadial and patient] angles with the generatrices-of the latter, stasaid grinding wheel and coinciding therewith during the grinding operations, means for movably supporting the said drill holder and also adapted to receive truing means for trimming the radial working face of said grinding wheel in said plane containing the axis of said drill when the latter is set in its holder, and only in said plane, and the said supporting means being further adapted to receive truing means for trimming the peripheral working face of said grinding wheel perpendicularly to said plane containing the axis of the drill in its holder and in such manner as to make said peripheral face tangent to the line of motion of the geometric center of the drill tip during the grinding operations, and the said supporting means including means for movably supporting said peripheral truing means from said machine frame in fixed space relation with respect to the plane of motion of the geometric center of the drill tip.

2. A finishing twist drill grinding machine as hereinbefore defined comprising, in combination, a frame, a cylindrical grinding wheel rotatably mounted on. said frame, said grinding wheel having radial and peripheral working faces, the radii of the former forming sharply defined right angles with the generatrices of the latter, a drill holder adapted to hold said drill with its axis lying in a movable plane at least parallel to that of the radial grinding face and coinciding therewith during the grinding operations, means for movably supporting and guiding saiddrill holder and also adapted to receive truing means for trimming the radial grinding face in said plane containing the axis of the drill in its holder and only in said plane, and adapted to receive truing means for trimming the peripheral grinding face perpendicularly tosaid plane containing the axis of the drill in its holder and in such manner as to make said peripheral grinding face tangent to the line of motion of the geometric center. of the drill tip during the grinding operations, the said supporting and guiding means being further adapted to allow simultaneous parallel translation of said drill holder and said radial grinding face truing means in two directions parallel to said radial grinding face and in one direction perpendicular to the same, and the aforementioned supporting and guiding means including means for movably supporting and guiding said peripheral truing means from said machine frame in fixed space relation with respect to the plane of motion of the geometric center of the drill tip, the said latter supporting and guiding means being adapted to allow si multaneous parallel translation of said peripheral truing means, of said radial truing means and of said drill holder in one direction parallel the grinding operations, a bracket member adapted to slide up and down on said guideways,

. lowerguideways supported by said bracket memand perpendicular to said radial grinding face, a lower sliding table adapted to translate on said lower guideways, upper guideways supported on said lower sliding table and parallel to said radial grinding face and perpendicular to said stationary guideways, an upper sliding table adapted totranslate on said upper guideways, a drill holder mounted on the said upper sliding table and adapted to hold said drill with itsaxis in' a movable plane at least parallel to that of the said radial grinding face and coinciding therewith during the grinding operations, the said upper sliding table being also adapted to receive truing means for trimming the said radial grinding face in said plane containing the axis of the drill in its holder, and only in said plane, and the said lower sliding table being also adapted to receive truing means for trimming the peripheral working face of said grinding wheel perpendicularly to said plane containing the axis of the drill in its holder and in such manner as to make said peripheral working face tangent to the line of motion of the geometric center of the drill tip during the grinding operations, means for adjustlngthe position of said bracket member on said stationary guideways, means for moving said lower sliding table on its guideways into the grinding position and, when necessary, for trimming the peripheral face of the grinding wheel, and means for moving said upper sliding table on its guideways for the grinding operations and, when necessary, for trimming the radial working face of said grinding wheel.

4. A finishing twist drill grinding machine ac- I cording to claim 3 comprising, in addition, removable abutment means for positioning'the drill axially in its holder in such manner as to locate the geometric center of the drill tip at a given predetermined distance above said upper sliding table.

5. A finishing twist drill grinding machine according to claim 3 comprising, in addition, removable abutment means for positioning the drill axially and radially in its holder in such manner as to locate the geometric center of the drill tip at a given predetermined distance above said upper sliding table and to set the blunt edge of the drill tip at a given predetermined angle with the radial working face of the grinding wheel.

6. A finishing twist drill grinding machine according to claim 3 comprising, in addition, removable abutment means for positioning the drill axially and radially in its holder in such manner as to locate the geometric'center of the drill tip at a given predetermined distance above said upper sliding table and to set the blunt edge of the drill tip at a given predetermined angle with the radial working face of the grinding wheel, and means associated'with said drill positioning means adapted to ensure the locking of said positioning means in a given position, in order to allow anumber of drillsto be sharpened unde identical conditions. 'I. A finishing twist drill grinding machine according to claim 3 in which said drill holder comprises means for revolving said drill around its own axis between grinding operations, without it being necessary to loosen the drill gripping 'means, or to displace the drill axially, or to move its axis with respect to the grinding wheel.

iii A finishing twist drill grinding machine according to claim 3 comprising micrometricallyadjustable stop means associated with said lower sliding table in such manner as to limit the travel of said lower table in the direction of the grinding wheel to that position in which the plane conm mm m mm m. z m. m a

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